215.2(A)(1) Requires a feeder to be sized at 125% of continuous load. NEC 250.21 allows heating loads to be calculated at 100% of calculated load. I have always used NEC 250.21. Now I am being told that a feeder that feeds a panel of only heaters exclusively needs to be sized at 125%. What is correct?
125% of continuous load
- Thread starter wyboy
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kwired
Electron manager
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- NE Nebraska
I think you got the wrong section, 250 is grounding and part 21 is AC systems 50 to 1000 volts not required to be grounded?
kwired
Electron manager
- Location
- NE Nebraska
Didn't read exactly what it says, but keep in mind 220 is load calculations (determining what the load is and may take into consideration the duty cycles of certain loads) and not about selecting conductor size.
wwhitney
Senior Member
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- Berkeley, CA
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What is the load?
For example, Article 424 "Fixed Electric Space-Heating Equipment" says in (2017) 424.3(B) "Branch-Circuit Sizing. Fixed electric space-heating equipment and motors shall be considered continuous load." As there is nothing comparable in 424 on feeders, that means you'd use a 125% continuous load factor for the branch circuits, but not for feeders supplying those branch circuits.
Cheers, Wayne
For example, Article 424 "Fixed Electric Space-Heating Equipment" says in (2017) 424.3(B) "Branch-Circuit Sizing. Fixed electric space-heating equipment and motors shall be considered continuous load." As there is nothing comparable in 424 on feeders, that means you'd use a 125% continuous load factor for the branch circuits, but not for feeders supplying those branch circuits.
Cheers, Wayne
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